1. Field of the invention
The present invention relates generally to vibrating gyroscopes and more particularly to a vibrating gyroscope applicable to navigation systems for suitably directing the movement of an object so that it will reach its intended destination by detecting its current position based on detection of the angular velocity thereof.
Description of the Related Art
A vibrating gyroscope in the prior art is shown in FIGS. 4A and 4B, wherein FIG. 4A illustrates a perspective view of the gyroscope, and FIG. 4B depicts a cross-section thereof along a line IVB--IVB of FIG. 4A. The prior art gyroscope 1 generally includes a vibrator 2. The vibrator 2 contains a vibrating reed type elongate vibrating member 3 of a square rod shape. The vibrating member 3 has a pair of opposed side walls, on which piezoelectric elements 4a and 4b each acting as an electromechanical driver are mounted at intermediate or midway positions of the side walls, respectively. Each of these piezoelectric drivers 4a, 4b consists of a piezoelectric layer 5 sandwiched between upper and lower electrodes 6. The vibrating member 3 also has another pair of opposed surfaces on which further piezoelectric elements 4c, 4d are formed at midway positions of the surfaces to serve as detectors. Each of these piezoelectric detectors 4c, 4d has a three-layered structure similar to that of the piezoelectric drivers 4a, 4b, including an intermediate piezoelectric layer 5 sandwiched between inner and outer electrodes 7 on both surfaces of the layer 5.
As shown in FIG. 4A, in the vibrating gyroscope 1, two separate support members 8 support the vibrator 2 at specific positions near two node points (nodes) of the vibrating member 3. The support members 8 are arranged so as to maximally enable the vibrating member 3 to exhibit free vibrations. Each support member 8 may be a metal wire bent in an L-shaped form, which is secured by soldering to the vibrating member 3. In this case, the vibrating member 3 is provided with transverse through-holes (not shown) extending in the vicinity of the nodes. Such through-holes are so formed as to extend, in parallel with each other, from one side wall of the vibrating member 3 toward the opposite side wall thereof. The vibrating member 3 is supported by inserting and adhering one end of each L-shaped support member 8 to a corresponding one of the through-holes. More specifically, one end portion of each support member 8 extends perpendicularly to the axis of the vibrating member 3 to be fixed thereto, while the other end of it extends downward to be bonded by adhesion to a support base 9, which may be attached to a casing structure (not shown), thereby to provide an L-shaped leg-like support assembly as shown in FIG. 4A.
The prior art vibrating gyroscope 1 is provided with an oscillating circuit (not shown) connected between the piezoelectric drivers 4a, 4b. Upon the application of an oscillatory current from the oscillator circuit, the piezoelectric drivers 4a, 4b cause the vibrating member 3 to vibrate under a bending mode in a direction perpendicular to the planes of the piezoelectric drivers 4a, 4b. Under such a condition, when the vibrating gyroscope 1 is rotating or spinning about its axis, for example, the Coriolis force acts in the direction at right angles to the direction of vibration. Due to the action of this Coriolis force, the vibrating member 3 varies in its direction of vibration and generates an output voltage across the piezoelectric detectors 4c, 4d. Since the output voltage is proportional to the bending amount in the direction perpendicular to the formation planes of the piezoelectric detectors 4c, 4d, the angular rotation velocity or speed of the vibrating gyroscope 1 can be found by detecting such output voltage.
However, the prior art vibrating gyroscope 1 shown in FIGS. 4A and 4B suffers from the problem that the mechanical support structure for the vibrating member 3 is bulky and complicated in configuration due to the fact that (i) the vibrating member 3 consists of a vibrating reed of elongate square rod shape, which requires the nodes of free vibration to be positioned midway between both ends of the vibrating member 3, (ii) any distortion caused by Coriolis force while the vibrating member 3 is rotating about its axis is produced in the direction perpendicular to that of distortion resulting from free vibration of the vibrating member 3, and (iii) the sensitivity of the vibrating gyroscope 1 is enhanced by arranging the mechanical support structure for the vibrating member 3 such that the degree of freedom increases with respect to two such orthogonal directions.
More specifically, with the prior art vibrating gyroscope 1 of FIGS. 4A and 4B, since it is required that the through-holes be formed in the vibrating member 3 at specific positions near the midway nodes thereof, allowing the first ends of the respective L-shaped support members 8 to be inserted for adhesion while having the second ends thereof bonded to the support base 9, the resulting gyroscope structure becomes undesirably complicated while rendering the assembly process therefor difficult. In other words, the advantages provided by the vibrating gyroscope 1 of FIGS. 4A and 4B do not come without accompanying drawbacks: the gyroscope configuration is massive and complicated in its mechanical support structure for the vibrator 2, which results in the support members being bulky, causing miniaturization or down-sizing of such a vibrator to be difficult when light weight and small size is needed. Another problem faced with the prior art vibrating gyroscope 1 is that, since the vibrator 2 is supported by use of both the support members 8 and the support base 9, the resultant cost for materials and for the assembly of such an increased number of structural members remains high, which may also provide a serious bar to the accomplishment of decreased manufacturing cost.